1. The Particulate Nature of Matter Flashcards
Describe the attractive forces in solids
Strong forces of attraction between particles, particles are packed very closely together in a fixed and regular pattern
Describe the attractive forces in liquids
Weaker attractive forces in liquids than in solids, particles are close together in an irregular, unfixed pattern
Describe the attractive forces in gases
No intermolecular forces, particles are in random movement and so there is no defined pattern
Describe the movement in solids
Atoms vibrate in position but can’t change position or move
Describe the movement in liquids
Particles can move and slide past each other which is why liquids adopt the shape of the container they’re in and also why they are able to flow
Describe the movement in gases
Particles are far apart and move quickly (around 500 m/s) in all directions, they collide with each other and with the sides of the container (this is how pressure is created inside a can of gas)
Describe the fixed volume and density in solids
solids have a fixed volume, shape and high density
Describe the fixed volume and density in liquids
Liquids have a fixed volume but not a fixed shape and have a moderate to high density
Describe the fixed volume and density in gases
No fixed volume, since there is a lot of space between the particles, gases can be compressed into a much smaller volume. Gases have low density
What change occurs during melting?
Melting is when a solid changes into a liquid
What does melting require?
Requires heat energy which transforms into kinetic energy, allowing the particles to move
When does melting occur?
Occurs at a specific temperature known as the melting point (m.p.) which is unique to each pure solid
What change occurs during boiling?
Boiling is when a liquid changes into a gas
What does boiling require?
Requires heat which causes bubbles of gas to form below the surface of a liquid, allowing for liquid particles to escape from the surface and within the liquid
When does boiling occur?
Occurs at a specific temperature known as the boiling point (b.p.) which is unique to each pure liquid
What change occurs during freezing?
Freezing is when a liquid changes into a solid
When does freezing occur?
This is the reverse of melting and occurs at exactly the same temperature as melting, hence the melting point and freezing point of a pure substance are the same. Water for example freezes and melts at 0ºC
What does freezing require?
Requires a significant decrease in temperature (or loss of thermal energy) and occurs at a specific temperature which is unique for each pure substance
What change occurs during evaporation?
When a liquid changes into a gas.
What is the difference between boiling and evaporation?
Evaporation occurs only at the surface of liquids where high energy particles can escape from the liquid’s surface at low temperatures, below the b.p. of the liquid
What increases the rate of evaporation?
The larger the surface area and the warmer the liquid/surface, the more quickly a liquid can evaporate
What is required for evaporation? (if anything)
No energy is required for evaporation to occur and it takes place over a range of temperatures
What change occurs during condensation?
When a gas changes into a liquid, usually on cooling
How does condensation occur (in terms of particles)?
When a gas is cooled its particles lose energy and when they bump into each other they lack the energy to bounce away again, instead they group together to form a liquid
What is required for condensation? (if anything)
No energy is required for condensation to occur and it takes place over a range of temperatures
What change occurs during sublimation?
When a solid changes directly into a gas
What example of solids can undergo sublimation?
This happens to only a few solids such as iodine or solid carbon dioxide
What is the reverse reaction of sublimation?
The reverse reaction also happens and is also called sublimation (sometimes called deposition or desublimation)
When does sublimation occurr?
Sublimation occurs at a specific temperature which is unique for a pure substance
In what type of motion are gaseous particles in?
Gaseous particles are in constant and random motion
What happens to gaseous particles when there is an increase in temperature?
An increase in temperature increases the kinetic energy of each particle, as the thermal energy is transformed to kinetic energy, so they move faster
What causes pressure in a container?
The pressure that a gas creates inside a closed container is produced by the gaseous particles hitting the inside walls of the container.
What is the effect of increasing temperature on pressure?
- As the temperature increases, the particles in the gas move faster, impacting the container’s walls more frequently
- Therefore an increase in temperature causes an increase in pressure
Brownian Motion definition
Brownian motion is defined as the random movement of particles in a liquid or a gas produced by large numbers of collisions with smaller, often invisible particles
What does the observation of brownian motion prove?
the correctness of the kinetic particle theory
Diffusion definition
This is the process by which different gases or different liquids mix and is due to the random motion of their particles
From where to where do diffusing particles move?
Diffusing particles move from an area of high concentration to an area of low concentration, till the concentration of particles is even
Does diffusion require energy?
NO
Diffusion happens on its own and no energy input is required although it occurs faster at higher temperatures
What is the basis of the kinetic theory of matter?
When substances are heated, the particles absorb thermal energy which is converted into kinetic energy
What happens when you heat a solid?
Heating a solid causes its particles to vibrate more and as the temperature increases, they vibrate so much that the solid expands until the structure breaks and the solid melts
What happens when you heat a liquid?
On further heating, the now liquid substance expands more and some particles at the surface gain sufficient energy to overcome the intermolecular forces and evaporate
What happens when the b.p. temperature is reached in a liquid?
When the b.p. temperature is reached, all the particles gain enough energy to escape and the liquids boils
What type of graph can be used to show how changes in temperature affect changes in state?
A heating curve - solid to gas
A cooling curve - gas tp solid
What is an example of Brownian Motion?
An example of Brownian motion is the observed jerky and erratic motion of smoke particles as they are hit by the unseen molecules in the air which can be seen under a microscope
What is the basic condition needed to show the Brownian process is occurring?
In all cases, larger and visible particles are caused to move by the random bombardment of smaller, invisible particles
In what state does diffusion happen the fastest?
Diffusion occurs much faster in gases than in liquids as gaseous particles move much quicker than liquid particles
Do gases diffuse at different rates at the same temperature?
YES
- At the same temperature, different gases do not diffuse at the same rate.
What causes the difference in the rate of diffusion in gases?
This is due to the difference in their relative molecular masses
At what relative molecular mass do gas particles diffuse the fastest?
Lighter gas particles can travel faster and hence further, therefore the lower its relative mass the faster a gas will diffuse
